1. Field of the Invention
The invention concerns an elastic support device for stator winding end turns of a rotating electrical machine, for turbo-alternators in particular.
2. Description of the prior art
Stator winding end turns 50 (FIG. 1) must be supported elastically because they are subject to stresses and deformation due to possible short-circuits, sudden fluctuations in current, thermal expansion and other causes.
Stator winding end turns 50 are supported by a cage 30 in the form of a plurality of rings concentric with the magnetic circuit and resting on insulative supports equiangularly distributed around the stator. The cage is fixed to the stator clamping plate by angle-brackets 37 usually of a magnetic stainless steel (see FIG. 1). A first side of the angle-brackets is fixed to the clamping plate with a damper screen between them. The second side is fixed to the insulative support of the cage. The flexibility of the angle-brackets gives the stator winding end turns the required elasticity.
The use of angle-brackets raises a number of problems. It is difficult to distribute them circumferentially on the clamping plate with sufficient accuracy. Some angle-brackets may break in operation because of the loads on them and the resulting asymmetry is prejudicial to proper operation of the machine. There is also some uncertainty as to the bearing engagement of the angle-brackets, any defective bearing engagement causing an offset and vibration of the winding.
An object of the device in accordance with the invention is to increase the mechanical strength of the cage and of the means retaining the stator winding end turns 50 by replacing the metal angle-brackets 37 used until now by a ring having a spring effect, i.e. an elastic ring.
Using a ring instead of angle-brackets means that the damper screen fixing function and the cage fixing function can be separated. The ring may be made from a magnetic stainless steel or from fiberglass impregnated with epoxy resin.
Another advantage of the new structure is the saving in terms of assembly time. The various components are also easier to assemble.